nss.go

Documentation: net

		 1  // Copyright 2015 The Go Authors. All rights reserved.
		 2  // Use of this source code is governed by a BSD-style
		 3  // license that can be found in the LICENSE file.
		 4  
		 5  //go:build aix || darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
		 6  // +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
		 7  
		 8  package net
		 9  
		10  import (
		11  	"errors"
		12  	"internal/bytealg"
		13  	"io"
		14  	"os"
		15  )
		16  
		17  // nssConf represents the state of the machine's /etc/nsswitch.conf file.
		18  type nssConf struct {
		19  	err		 error									// any error encountered opening or parsing the file
		20  	sources map[string][]nssSource // keyed by database (e.g. "hosts")
		21  }
		22  
		23  type nssSource struct {
		24  	source	 string // e.g. "compat", "files", "mdns4_minimal"
		25  	criteria []nssCriterion
		26  }
		27  
		28  // standardCriteria reports all specified criteria have the default
		29  // status actions.
		30  func (s nssSource) standardCriteria() bool {
		31  	for i, crit := range s.criteria {
		32  		if !crit.standardStatusAction(i == len(s.criteria)-1) {
		33  			return false
		34  		}
		35  	}
		36  	return true
		37  }
		38  
		39  // nssCriterion is the parsed structure of one of the criteria in brackets
		40  // after an NSS source name.
		41  type nssCriterion struct {
		42  	negate bool	 // if "!" was present
		43  	status string // e.g. "success", "unavail" (lowercase)
		44  	action string // e.g. "return", "continue" (lowercase)
		45  }
		46  
		47  // standardStatusAction reports whether c is equivalent to not
		48  // specifying the criterion at all. last is whether this criteria is the
		49  // last in the list.
		50  func (c nssCriterion) standardStatusAction(last bool) bool {
		51  	if c.negate {
		52  		return false
		53  	}
		54  	var def string
		55  	switch c.status {
		56  	case "success":
		57  		def = "return"
		58  	case "notfound", "unavail", "tryagain":
		59  		def = "continue"
		60  	default:
		61  		// Unknown status
		62  		return false
		63  	}
		64  	if last && c.action == "return" {
		65  		return true
		66  	}
		67  	return c.action == def
		68  }
		69  
		70  func parseNSSConfFile(file string) *nssConf {
		71  	f, err := os.Open(file)
		72  	if err != nil {
		73  		return &nssConf{err: err}
		74  	}
		75  	defer f.Close()
		76  	return parseNSSConf(f)
		77  }
		78  
		79  func parseNSSConf(r io.Reader) *nssConf {
		80  	slurp, err := readFull(r)
		81  	if err != nil {
		82  		return &nssConf{err: err}
		83  	}
		84  	conf := new(nssConf)
		85  	conf.err = foreachLine(slurp, func(line []byte) error {
		86  		line = trimSpace(removeComment(line))
		87  		if len(line) == 0 {
		88  			return nil
		89  		}
		90  		colon := bytealg.IndexByte(line, ':')
		91  		if colon == -1 {
		92  			return errors.New("no colon on line")
		93  		}
		94  		db := string(trimSpace(line[:colon]))
		95  		srcs := line[colon+1:]
		96  		for {
		97  			srcs = trimSpace(srcs)
		98  			if len(srcs) == 0 {
		99  				break
	 100  			}
	 101  			sp := bytealg.IndexByte(srcs, ' ')
	 102  			var src string
	 103  			if sp == -1 {
	 104  				src = string(srcs)
	 105  				srcs = nil // done
	 106  			} else {
	 107  				src = string(srcs[:sp])
	 108  				srcs = trimSpace(srcs[sp+1:])
	 109  			}
	 110  			var criteria []nssCriterion
	 111  			// See if there's a criteria block in brackets.
	 112  			if len(srcs) > 0 && srcs[0] == '[' {
	 113  				bclose := bytealg.IndexByte(srcs, ']')
	 114  				if bclose == -1 {
	 115  					return errors.New("unclosed criterion bracket")
	 116  				}
	 117  				var err error
	 118  				criteria, err = parseCriteria(srcs[1:bclose])
	 119  				if err != nil {
	 120  					return errors.New("invalid criteria: " + string(srcs[1:bclose]))
	 121  				}
	 122  				srcs = srcs[bclose+1:]
	 123  			}
	 124  			if conf.sources == nil {
	 125  				conf.sources = make(map[string][]nssSource)
	 126  			}
	 127  			conf.sources[db] = append(conf.sources[db], nssSource{
	 128  				source:	 src,
	 129  				criteria: criteria,
	 130  			})
	 131  		}
	 132  		return nil
	 133  	})
	 134  	return conf
	 135  }
	 136  
	 137  // parses "foo=bar !foo=bar"
	 138  func parseCriteria(x []byte) (c []nssCriterion, err error) {
	 139  	err = foreachField(x, func(f []byte) error {
	 140  		not := false
	 141  		if len(f) > 0 && f[0] == '!' {
	 142  			not = true
	 143  			f = f[1:]
	 144  		}
	 145  		if len(f) < 3 {
	 146  			return errors.New("criterion too short")
	 147  		}
	 148  		eq := bytealg.IndexByte(f, '=')
	 149  		if eq == -1 {
	 150  			return errors.New("criterion lacks equal sign")
	 151  		}
	 152  		lowerASCIIBytes(f)
	 153  		c = append(c, nssCriterion{
	 154  			negate: not,
	 155  			status: string(f[:eq]),
	 156  			action: string(f[eq+1:]),
	 157  		})
	 158  		return nil
	 159  	})
	 160  	return
	 161  }
	 162
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